In general, a washing machine performs washing by rotating a drum having laundries therein through a driving force transmitted by a motor in a state where detergent and the laundry are mixedly loaded into a drum.
Recently, a drum washing machine has been preferably used, which washes the laundry by using friction force between a rotating drum and the laundry, because the drum washing machine has a washing effect as if the laundry were scrubbed and washed by human hands and another washing effect that the laundry may not be entangled.
The drum washing machine is classified by a driving method into an indirect-motor-drive type and a direct-motor drive type. According to the indirect-motor drive type washing machine, the driving force of motor is indirectly transmitted to a drum through a motor pulley and a belt wound around a drum pulley. According to the direct-motor-drive type drum washing machine, the driving fore of motor is directly transmitted to a drum, because a rotor of a BLDC motor is directly connected with the drum.
Referring to FIG. 1, a conventional direct-drive motor type drum washing machine will be schematically described.
FIG. 1 is a longitudinal sectional view illustrating a structure of a conventional drum washing machine. The conventional drum washing machine includes a cabinet 1 defining an exterior thereof, a tub 2 mounted within the cabinet 1 with a front side opened and a drum 3 rotatably mounted in an inner center of the tub 2.
Moreover, a motor 47 having a stator 6 and a rotor 5 is mounted in a rear wall of the tub 2. The stator 6 is secured to a rear wall of the tub 2 and the rotor 5 passes through the tub 2 with surrounding the stator 6 and is connected with the drum 3 by a shaft 4.
Together with that, a tub supporter in the same appearance as an exterior of the rear wall of the tub 2 is provided between the rear wall of the tub 2 and the stator 6, and fastened to the rear wall of the tub 2 to support the load of the stator 6 when fastening the stator 6. Also, the tub supporter is made of metal to maintain the concentricity of the stator 6.
Meanwhile, a door 21 is coupled to a front side of the cabinet 1, and a gasket 22 is provided between the door 21 and the tub 2.
In addition, a hanging spring 23 is provided between an upper inner surface of the cabinet 1 and an upper circumferential surface of the tub 2 to support the tub 2. Also, a friction damper 24 is provided between an inner lower surface of the cabinet 1 and a lower portion of the outer circumferential surface of the tub 2 to dampen the vibration of tub 2 generated in spinning.
Referring to FIG. 2, a bearing housing 7 having a hollow 55 formed in a center thereof is inserted into the tub 2. The shaft 4 of the motor 47 passes through the hollow 55.
At that time, the bearing housing 7 is made of aluminum alloy and formed as one body with the rear wall of the tub 2 by being inserted into the rear wall of the tub 2 when injection-molding the tub 2 with plastic resin.
Also, the beating housing 7 has bearings 600a and 600b secured to an opposite she sides of the hollow 55.
Also, a bushing 11 made of brass, which is rust-resistant, is provided at a front bearing 600a secured to the drum 3, and a sealing member 12 is provided on an outer surface of the bushing 11 to prevent moisture from percolating toward the front bearing 600a. 
However, the conventional drum washing machine has following problems.
The conventional drum washing machine has a problem that moisture regardless of a small amount may percolate toward the front bearing 600a of the drum 3 even though the sealing member 12, because the power is applied to rotate the drum 3 and wash water is filled up within the tub 2 in the beginning of the washing process.
Especially, if the small amount of the percolating moisture is easily changed into water because of the high temperature of the portion around the shaft caused by the high speed rotation of the drum 3, the water could be pooled in a portion adjacent to the front bearing 600a. 
In that case, the metal around the front bearing 600a may become rusty due to the percolating moisture or water and also oil may be mixed with the water, thereby deteriorating durability or generating noise.